The present invention relates to testing the internal geometry of tubes or pipes under utilization of a measuring mandrel-like probe movable through the tube or pipe by means of pneumatics and including a device connected to a source of pressurized air and being provided to receive the measuring mandrel to have the mandrel propelled through the tube or pipe to be tested.
Measuring the geometry of a tube or pipe under utilization of a measuring mandrel as mentioned requires that certain rules of the American Petroleum Institute are to be observed. The testing is made difficult by the fact that the testing period has to fit in the production cycle. Also, following the insertion of the measuring device into the tube or pipe from one end and catching it at the other end it must be in some way returned to a position for insertion into the next pipe which will assume a position just as the previous one had during say a continuous mode of production.
It has been suggested in U.S. Pat. No. 4,354,379 to provide a net at the exit end of the tube or pipe to capture the measuring mandrel in that fashion. But how the measuring mandrel is then to be returned is not detailed in that reference. In accordance with another proposal it is suggested to capture the mandrel by means of a cushioning device when it is still at least in parts in the tube or pipe. Through suction the mandrel is then returned back to its launching station. This proposal is disadvantaged by the fact that the advance of the measuring mandrel is very nonuniform. Moreover, should for some reason a measuring mandrel get caught in the interior of a tube namely because the tube has two small an inner diameter, one has to remove the tube from the test stand and push the mandrel out of the tube by means of rods or the like because pneumatics cannot be expected to work anymore once the mandrel is stuck.